To translate between X.25 and another protocol, refer to the chapter "Configuring Protocol Translation and Virtual Asynchronous Devices" in the Cisco IOS Terminal Services Configuration Guide.

For X.25 and LAPB configuration information and examples, refer to the "Configuring X.25 and LAPB" chapter in the Cisco IOS Wide-Area Networking Configuration Guide.

access-class (X.25)

To configure an incoming access class on virtual terminals, use the access-class (X.25) line configuration command.

access-class access-list-number in

Syntax Description

access-list-number

An integer from 1 to 199 that you select for the access list.

in

Restricts incoming connections between a particular access server and the addresses in the access list.

Defaults

No incoming access class is defined.

Command Modes

Line configuration

Command History

Release

Modification

10.3

This command was introduced.

Usage Guidelines

The access list number is used for both incoming Transmission Control Protocol (TCP) access and incoming packet assembler/disassembler (PAD) access.

In the case of TCP access, the access server uses the IP access list defined with the access-list command.

For incoming PAD connections, the same numbered X.29 access list is referenced. If you only want to have access restrictions on one of the protocols, you can create an access list that permits all addresses for the other protocol.

Examples

The following example configures an incoming access class on virtual terminal line 4. For information on the line vty command see the publication Configuring the Route Processor for the Catalyst 8540 and Using Flash Memory Cards.

Related Commands

bfe

This command is no longer supported.

clear x25

To restart an X.25 service or Connection-Mode Network Service (CMNS), to clear a switched virtual circuit (SVC), or to reset a permanent virtual circuit (PVC), use the clear x25 privileged EXEC command.

(Optional) SVC or PVC number, in the range 1 to 4095. If specified, the SVC is cleared or the PVC is reset. If not specified, the X.25 or CMNS service is restarted.

dlci number

(Optional) When combined with a serial interface number, it triggers a restart event for an Annex G logical X.25 VC.

Command Modes

Privileged EXEC

Command History

Release

Modification

11.2

This command was introduced. This command replaces the clear x25-vc command, which first appeared in Cisco IOS Release 8.3.

12.0(3)T

Annex G restart or clear options were added.

Usage Guidelines

This command form is used to disrupt service forcibly on an individual circuit or on all circuits using a specific X.25 service or CMNS service.

If this command is used without the vc-number value, a restart event is initiated, which implicitly clears all SVCs and resets all PVCs.

This command allows the option of restarting an Annex G connection per data-link connection identifier (DLCI) number, clearing all X.25 connections, or clearing a specific X.25 logical circuit number on that Annex G link.

Examples

The following example clears the SVC or resets the PVC specified:

clear x25 serial 0 1

The following example forces an X.25 restart, which implicitly clears all SVCs and resets all PVCs using the interface:

clear x25 serial 0

The following example restarts the specified CMNS service (if active), which implicitly clears all SVCs using the service:

clear x25 ethernet 0 0001.0002.0003

The following example clears the specified DLCI Annex G connection (40) from the specified interface:

Syntax Description

Command Modes

EXEC

Command History

Release

Modification

11.2

This command was introduced.

Usage Guidelines

Each SVC or PVC supported by the XOT service uses a TCP connection to communicate X.25 packets. A TCP connection is uniquely identified by the data quartet: remote IP address, remote TCP port, local IP address, and local TCP port. This command form is used to forcibly disrupt service on an individual XOT circuit.

XOT connections are sent to TCP port 1998, so XOT connections originated by the router will have that remote port number, and connections received by the router will have that local port number.

Examples

The following command will clear or reset, respectively, the SVC or PVC using the TCP connection identified:

Syntax Description

(Optional) Specifies use of multiple local-area network (LAN) protocols to be carried on the LAPB line.

protocol

(Optional) A single protocol to be carried on the LAPB line. A single protocol can be one of the following: apollo, appletalk, clns (ISO CLNS), decnet, ip, ipx (Novell IPX), vines, and xns.IP is the default protocol.

Defaults

The default serial encapsulation is High-Level Data Link Control (HDLC). You must explicitly configure a LAPB encapsulation method.

DTE operation is the default LAPB mode. IP is the default protocol.

Command Modes

Interface configuration

Command History

Release

Modification

10.0

This command was introduced.

10.3

The following keywords and argument were introduced:

•dte

•dce

•multi

•protocol

Usage Guidelines

LAPB encapsulations are appropriate only for private connections, where you have complete control over both ends of the link. Connections to X.25 networks should use an X.25 encapsulation configuration, which operates the X.25 Layer 3 protocol above a LAPB Layer 2.

One end of the link must be a logical DCE device, and the other end a logical DTE device. (This assignment is independent of the interface's hardware DTE or DCE identity.)

Both ends of the LAPB link must specify the same protocol encapsulation.

LAPB encapsulation is supported on serial lines configured for dial-on-demand routing (DDR). It can be configured on DDR synchronous serial and ISDN interfaces and on DDR dialer rotary groups. It is not supported on asynchronous dialer interfaces.

A single-protocol LAPB encapsulation exchanges datagrams of the given protocol, each in a separate LAPB information frame. You must configure the interface with the protocol-specific parameters needed—for example, a link that carries IP traffic will have an IP address defined for the interface.

A multiprotocol LAPB encapsulation can exchange any or all of the protocols allowed for a LAPB interface. It exchanges datagrams, each in a separate LAPB information frame. Two bytes of protocol identification data precede the protocol data. You need to configure the interface with all the protocol-specific parameters needed for each protocol carried.

Beginning with Cisco IOS Release 11.0, multiprotocol LAPB encapsulation supports transparent bridging. This feature requires use of the encapsulation lapbmulti command followed by the bridge-group command, which identifies the bridge group associated with multiprotocol LAPB encapsulation. This feature does not support use of the encapsulation lapbprotocol command with a bridge keyword.

Command Modes

Interface configuration

Command History

Release

Modification

10.0

This command was introduced.

10.3

The following keywords were added:

•dte

•dce

•ddn

•bfe

•ietf

Usage Guidelines

One end of an X.25 link must be a logical DCE device and the other end a logical DTE device. (This assignment is independent of the interface's hardware DTE or DCE identity.) Typically, when connecting to a public data network (PDN), the customer equipment acts as the DTE device and the PDN attachment acts as the DCE.

Cisco has long supported the encapsulation of a number of datagram protocols, using a standard means when available and a proprietary means when necessary. More recently the IETF adopted a standard, RFC 1356, for encapsulating most types of datagram traffic over X.25. X.25 interfaces use Cisco's traditional method unless explicitly configured for IETF operation; if the ietf keyword is specified, that standard is used unless Cisco's traditional method is explicitly configured. For details see the x25 map command.

You can configure a router attaching to the DDN or to a BFE device to use their respective algorithms to convert between IP and X.121 addresses by using the ddn or bfe option, respectively. An IP address must be assigned to the interface, from which the algorithm will generate the interface's X.121 address. For proper operation, this X.121 address must not be modified.

A router DDN attachment can operate as either a DTE or a DCE device. A BFE attachment can operate only as a DTE device. The ietf option is not available if either the ddn or bfe option is selected.

Examples

The following example configures the interface for connection to a BFE device:

interface serial 0

encapsulation x25 bfe

Related Commands

lapb interface-outage

To specify the period for which a link will remain connected, even if a brief hardware outage occurs (partial Link Access Procedure, Balanced [LAPB] T3 timer functionality), use the lapb interface-outage interface configuration command.

lapb interface-outage milliseconds

Syntax Description

milliseconds

Number of milliseconds (ms) a hardware outage can last without the protocol disconnecting the service.

Defaults

0 ms, which disables this feature.

Command Modes

Interface configuration

Command History

Release

Modification

10.0

This command was introduced.

Usage Guidelines

If a hardware outage lasts longer than the LAPB hardware outage period you select, normal protocol operations will occur. The link will be declared down, and when it is restored, a link setup will be initiated.

Examples

The following example sets the interface outage period to 100 ms. The link remains connected for outages equal to or shorter than that period.

Sets the LAPB T4 idle timer, after which time a poll packet is sent to determine state of an unsignaled failure on the link.

lapb k

To specify the maximum permissible number of outstanding frames, called the windowsize, use the lapb k interface configuration command.

lapb k window-size

Syntax Description

window-size

Frame count. It can be a value from 1 to the modulo size minus 1 (the maximum is 7 if the modulo size is 8; it is 127 if the modulo size is 128).

Defaults

7 frames

Command Modes

Interface configuration

Command History

Release

Modification

10.0

This command was introduced.

Usage Guidelines

If the window size is changed while the protocol is up, the new value takes effect only when the protocol is reset. You will be informed that the new value will not take effect immediately.

When using the Link Access Procedure, Balanced (LAPB) modulo 128 mode (extended mode), you must increase the window parameter k to send a larger number of frames before acknowledgment is required. This increase is the basis for the router's ability to achieve greater throughput on high-speed links that have a low error rate.

Syntax Description

Defaults

Modulo 8

Command Modes

Interface configuration

Command History

Release

Modification

10.0

This command was introduced.

Usage Guidelines

The modulo parameter determines which of LAPB's two modes is to be used. The modulo values derive from the fact that basic mode numbers information frames between 0 and 7, whereas extended mode numbers them between 0 and 127. Basic mode is widely available and is sufficient for most links. Extended mode is an optional LAPB feature that may achieve greater throughput on high-speed links that have a low error rate.

The LAPB operating mode may be set on X.25 links as well as LAPB links. The X.25 modulo is independent of the LAPB layer modulo. Both ends of a link must use the same LAPB mode.

When using modulo 128 mode, you must increase the window parameter k to send a larger number of frames before acknowledgment is required. This increase is the basis for the router's ability to achieve greater throughput on high-speed links that have a low error rate.

If the modulo value is changed while the protocol is up, the new value takes effect only when the protocol is reset. You will be informed that the new value will not take effect immediately.

Examples

The following example configures a high-speed X.25 link to use LAPB's extended mode:

Related Commands

Specifies the maximum permissible number of outstanding frames, called the window size.

lapb n1

To specify the maximum number of bits a frame can hold (the Link Access Procedure, Balanced [LAPB] N1 parameter), use the lapb n1 interface configuration command.

lapb n1 bits

Syntax Description

bits

Maximum number of bits in multiples of eight. The minimum and maximum range is dynamically set. Use the question mark (?) to view the range.

Defaults

The largest (maximum) value available for the particular interface is the default. The Cisco IOS software dynamically calculates N1 whenever you change the maximum transmission unit (MTU), the L2/L3 modulo, or compression on a LAPB interface.

Command Modes

Interface configuration

Command History

Release

Modification

10.0

This command was introduced.

Usage Guidelines

The Cisco IOS software uses the following formula to determine the minimum N1 value:

The Cisco IOS software uses the following formula to determine for the maximum N1 value:

(hardware MTU + LAPB overhead + X.25 overhead + 2 bytes of CRC) * 8

LAPB overhead is 2 bytes for modulo 8 and 3 bytes for modulo 128.

X.25 overhead is 3 bytes for modulo 8 and 4 bytes for modulo 128.

You need not set N1 to an exact value to support a particular X.25 data packet size. The N1 parameter prevents the processing of any huge frames that result from a "jabbering" interface, an unlikely event.

In addition, the various standards bodies specify that N1 be given in bits rather than bytes. While some equipment can be configured in bytes or will automatically adjust for some of the overhead information present, Cisco devices are configured using the true value, in bits, of N1.

You cannot set the N1 parameter to a value less than that required to support an X.25 data packet size of 128 bytes. All X.25 implementations must be able to support 128-byte data packets. Moreover, if you configure N1to be less than 2104 bits, you receive a warning message that X.25 might have problems because some nondata packets can use up to 259 bytes.

You cannot set the N1parameter to a value larger than the default unless the hardware MTU size is first increased.

The X.25 software accepts default packet sizes and calls that specify maximum packet sizes greater than those the LAPB layer supports, but negotiates the calls placed on the interface to the largest value that can be supported. For switched calls, the packet size negotiation takes place end-to-end through the router so the call will not have a maximum packet size that exceeds the capability of either of the two interfaces involved.

Caution The LAPB N1 parameter provides little benefit beyond the interface MTU and can easily cause link failures if misconfigured. Cisco recommends that this parameter be left at its default value.

Examples

The following example shows how to use the question mark (?) command to display the minimum and maximum N1 value. In this example, X.25 encapsulation has both the LAPB and X.25 modulo set to 8. Any violation of this N1 range results in an "Invalid input" error message.

Sets the LAPB T4 idle timer, after which time a poll packet is sent to determine state of an unsignaled failure on the link.

lapb protocol

The lapb protocol command has been replaced by the [protocol | multi] option of the encapsulation lapb command. See the description of the [protocol | multi] option of the encapsulation lapb command earlier in this chapter for more information.

lapb t1

To set the retransmission timer period (the Link Access Procedure, Balanced [LAPB] T1 parameter), use the lapb t1 interface configuration command.

lapb t1 milliseconds

Syntax Description

milliseconds

Time in milliseconds. It can be a value from 1 to 64000.

Defaults

3000 ms

Command Modes

Interface configuration

Command History

Release

Modification

10.0

This command was introduced.

Usage Guidelines

The retransmission timer determines how long a transmitted frame can remain unacknowledged before the LAPB software polls for an acknowledgment. The design of the LAPB protocol specifies that a frame is presumed to be lost if it is not acknowledged within T1; a T1 value that is too small may result in duplicated control information, which can severely disrupt service.

To determine an optimal value for the retransmission timer, use the ping privileged EXEC command to measure the round-trip time of a maximum-sized frame on the link. Multiply this time by a safety factor that takes into account the speed of the link, the link quality, and the distance. A typical safety factor is 1.5. Choosing a larger safety factor can result in slower data transfer if the line is noisy. However, this disadvantage is minor compared to the excessive retransmissions and effective bandwidth reduction caused by a timer setting that is too small.

Syntax Description

Time in milliseconds. It can be a value from 1 to 32000. Default is 0 ms (disabled) and the recommended setting.

Defaults

0 ms (disabled), which means that the software will send an acknowledgement as quickly as possible.

Command Modes

Interface configuration

Command History

Release

Modification

12.0

This command was introduced.

Usage Guidelines

The explicit acknowledge deferral timer determines the time that the software waits before sending an explicit acknowledgement. The acknowledgement is piggybacked with the data, unless there is no data and then an explicit acknowledgement is sent when the timer expires.

Caution It is usually not necessary (or recommended) to set the LAPB T2 timer, but if there is a requirement, it must be set to a value smaller than that set for the LAPB T1 timer; see the ITU X.25 specifications for details.

Command History

Usage Guidelines

Examples

The following example will poll the other end of an active link if it has been 10 seconds since the last frame was received. If the far host has failed, the service will be declared down after n2 tries are timed out.

Sets the LAPB T4 idle timer, after which time a poll packet is sent to determine state of an unsignaled failure on the link.

service pad

To enable all packet assembler/disassembler (PAD) commands and connections between PAD devices and access servers, use the service pad global configuration command. To disable this service, use the no form of this command.

service pad[cmns][from-xot][to-xot]

no service pad[cmns][from-xot][to-xot]

Syntax Description

cmns

(Optional) Specifies sending and receiving PAD calls over CMNS.

from-xot

(Optional) Accepts XOT to PAD connections.

to-xot

(Optional) Allows outgoing PAD calls over XOT.

Defaults

All PAD commands and associated connections are enabled. PAD services over XOT or CMNS are not enabled.

Command Modes

Global configuration

Command History

Release

Modification

10.0

This command was introduced.

11.3

The cmns keyword was added.

Usage Guidelines

The options from-xot and to-xot enable PAD calls to destinations that are not reachable over physical X.25 interfaces, but instead over TCP tunnels. This feature is known as PAD over XOT (X.25 over TCP).

Examples

If service pad is disabled, the EXEC pad command and all PAD related configurations, such as X.29, are unrecognized, as shown in the following example:

Router(config)# noservice pad

Router(config)# x29?

% Unrecognized command

Router(config)# exit

Router# pad ?

% Unrecognized command

If service pad is enabled, the EXEC pad command and access to an X.29 configuration are granted as shown in the following example:

service pad from-xot

To permit incoming X.25 over TCP (XOT) calls to be accepted as a packet assembler/disassembler (PAD) session, use the service pad from-xot global configuration command. To disable this service, use the no form of this command.

service pad from-xot

no service pad from-xot

Syntax Description

This command has no arguments or keywords.

Defaults

Incoming XOT connections are ignored.

Command Modes

Global configuration

Command History

Release

Modification

11.2

This command was introduced.

Usage Guidelines

If service pad from-xot is enabled, the calls received using the XOT service may be accepted for processing a PAD session.

Examples

The following example prevents incoming XOT calls from being accepted as a PAD session:

show cmns

Effective with Cisco IOS Release 11.3, this command is no longer available.

show x25 context

To view operating configuration status details of an X.25 link, use the show x25 context EXECcommand.

show x25 context [interface numberdlcinumber]

Syntax Description

interface number

(Optional) Specific logical X.25 virtual circuit interface.

dlcinumber

(Optional) Specific DLCI link.

Command Modes

EXEC

Command History

Release

Modification

12.0(3)T

This command was introduced.

12.1(5)T

This command was modified to display information about X.25 Failover.

Examples

The following is sample output from the show x25 context command:

Router# show x25 context

Serial1 DLCI 20

PROFILE DCE, address <none>, state R1, modulo 8, timer 0

Defaults: idle VC timeout 0

input/output window sizes 2/2, packet sizes 128/128

Timers: T10 60, T11 180, T12 60, T13 60

Channels: Incoming-only none, Two-way 1-1024, Outgoing-only none

RESTARTs 1/0 CALLs 0+0/0+0/0+0 DIAGs 0/0

LAPB DCE, state CONNECT, modulo 8, k 7, N1 12056, N2 20

T1 3000, T2 0, interface outage (partial T3) 0, T4 0

VS 7, VR 6, tx NR 6, Remote VR 7, Retransmissions 0

Queues: U/S frames 0, I frames 0, unack. 0, reTx 0

IFRAMEs 111/118 RNRs 0/0 REJs 0/0 SABM/Es 14/1 FRMRs 0/0 DISCs 0/0

The following is sample output from the show x25 context command when the X.25 Failover feature is configured. The "Fail-over delay" field appears when the primary interface has gone down and come back up again. The number of seconds indicates the time remaining until the secondary interface will reset.

If state is R2 or R3, the interface is awaiting acknowledgment of a Restart packet.

modulo

Modulo packet sequence numbering scheme.

timer

Interface timer value (zero unless the interface state is R2 or R3).

Defaults: idle VC timeout

Inactivity time before clearing VC.

input/output window sizes

Default window sizes (in packets) for the interface. The x25 facility interface configuration command can be used to override these default values for the switched virtual circuits originated by the router.

packet sizes

Default maximum packet sizes (in bytes) for the interface. The x25 facility interface configuration command can be used to override these default values for the switched virtual circuits originated by the router.

Timers

Values of the X.25 timers:

T10 through T13 for a DCE device

T20 through T23 for a DTE device

Channels

Virtual circuit ranges for this interface.

RESTARTs

Restart packet statistics for the interface using the format Sent/Received.

Related Commands

Configures an X.25 profile without allocating any hardware-specific information.

show x25 cug

To display information about all closed user groups (CUGs) or specific CUGs (defined by the local or network CUG number), use the show x25 cug EXEC command.

show x25 cug {local-cugnumber | network-cugnumber}

Syntax Description

local-cug

Locally significant CUG identifier.

number

Local CUG number (0 to 9999).

network-cug

Network translated CUG identifier.

number

Network CUG number (0 to 9999).

Command Modes

EXEC

Command History

Release

Modification

12.0(7)T

This command was introduced.

12.1(5)T

This command was modified to show information about CUG selection facility suppression.

Usage Guidelines

You must designate either the local-cug or the network-cug keyword with this command. Within these designations you can view all CUGs or a specific CUG defined by its local or network CUG identifier.

Examples

CUG Selection Facility Suppress Option Example

The following is sample output for the show x25 cug command when CUG selection facility is suppressed for all CUGs on serial interface 1/2 and for the preferential CUG on the X.25 profile named "cug".

Router# show x25 cug local-cug

X.25 Serial1/2, 2 CUGs subscribed with no public access

CUG selection facility suppressed for all CUGs

local-cug 100 <-> network-cug 10

local-cug 1 <-> network-cug 11

PROFILE cug, 2 CUGs subscribed with incoming public access

CUG selection facility suppressed for preferential CUG

local-cug 0 <-> network-cug 0 , preferential

local-cug 100 <-> network-cug 100

local-cug 200 <-> network-cug 200

Local CUG Example

The following is sample output from the show x25 cug local-cug command, displaying information about all local CUGs on X.25 serial interface 0. Four CUGs have been subscribed to on serial interface 0, and they all have been configured for incoming and outgoing public access.

show x25 hunt-group

To display hunt groups and view detailed interface statistics and distribution methods, use the show x25 hunt-group EXEC command.

show x25 hunt-group [name]

Syntax Description

name

(Optional) Displays the specific hunt group named.

Command Modes

EXEC

Command History

Release

Modification

12.0(3)T

This command was introduced.

12.0(5)T

The command output status field was modified to include "unoperational" as a type of interface status.

Usage Guidelines

Use the clear counters or the clear x25 commands in EXEC mode to clear the count of VCs in use in the "status" field and the number of bytes of data transmitted and received in the "traffic" field. Since the "uses" field is a hunt-group-specific counter, it will not be cleared using the clear counters or clear x25 commands. The "uses" field is only cleared at boot time or when the hunt group is defined.

Type and address of the higher-level protocol(s) mapped to the remote host. Bridge maps do not have a higher-level address; all bridge datagrams are sent to the mapped X.121 address. Connectionless Network Service (CLNS) maps refer to a configured neighbor as identified by the X.121 address.

PERMANENT

Address-mapping type that has been configured for the interface in this entry. Possible values include the following:

•CONSTRUCTED—Derived with the DDN or BFE address conversion scheme.

•PERMANENT—Map was entered with the x25 map interface configuration command.

•PVC—Map was configured with the x25 pvc interface command.

•TEMPORARY—A temporary map was created for an incoming unconfigured CMNS connection.

BROADCAST

If any options are configured for an address mapping, they are listed; the example shows a map that is configured to forward datagram broadcasts to the mapped host.

2 VCs:

If the map has any active virtual circuits, they are identified.

3 4*

Identifies the circuit number of the active virtual circuits. The asterisk (*) marks the virtual circuit last used to send data.

Note that a single protocol virtual circuit can be associated with a multiprotocol map.

show x25 profile

To view details of X.25 profiles on your router, use the show x25 profile command in EXEC mode.

show x25 profile[name]

Syntax Description

name

(Optional) Name of X.25 profile.

Command Modes

EXEC

Command History

Release

Modification

12.0(3)T

This command was introduced.

Examples

The following is sample output from the show x25 profile command, showing all profiles configured on the same interface. When the X.25 profile name is not specified, the output shows all configured profiles for that interface.

If state is R2 or R3, the interface is awaiting acknowledgment of a Restart packet.

modulo

Value that determines the packet sequence numbering scheme used.

timer

Interface timer value (zero unless the interface state is R2 or R3).

Defaults: idle VC timeout

Inactivity time before clearing virtual circuit (VC).

input/output window sizes

Default window sizes (in packets) for the interface. The x25 facility interface configuration command can be used to override these default values for the switched virtual circuits originated by the router.

packet sizes

Default maximum packet sizes (in bytes) for the interface. The x25 facility interface configuration command can be used to override these default values for the switched virtual circuits originated by the router.

Destination to which the router will forward a call; X.25 destinations identify an interface; CMNS destinations identify an interface and host MAC address; XOT destinations either identify up to six IP addresses (#2), or the x25 route pattern for retrieving up to six IP addresses from the DNS (#3 and #4).

The connectivity information displayed will vary according to the traffic carried by the virtual circuit. For multiprotocol circuits, the output varies depending on the number and identity of the protocols mapped to the X.121 address and the encapsulation method selected for the circuit.

Examples

Encapsulated Traffic Example

The following is sample output from the show x25 vc command used on an encapsulated traffic circuit:

Router# show x25 vc 1024

SVC 1024, State: D1, Interface: Serial0

Started 0:00:31, last input 0:00:31, output 0:00:31

Connects 170090 <-->

compressedtcp 172.20.170.90

ip 172.20.170.90

Call PID multi, Data PID ietf

Reverse charged

Window size input: 2, output: 2

Packet size input: 128, output: 128

PS: 5 PR: 5 ACK: 4 Remote PR: 5 RCNT: 1 RNR: FALSE

Window is closed

P/D state timeouts: 0 Timer (secs): 0

data bytes 505/505 packets 5/5 Resets 0/0 RNRs 0/0 REJs 0/0 INTs 0/0

Table 49 describes the fields shown in the sample output that are typical for virtual circuits.

Table 49 show x25 vc Field Descriptions

Field

Description

SVC n or PVC n

Identifies the type of virtual circuit (switched or permanent) and its LCN (also called its "virtual circuit number").

State

State of the virtual circuit (which is independent of the states of other virtual circuits); D1 is the normal ready state. See the International Telecommunication Union Telecommunication Standardization Sector (ITU-T)1 X.25 Recommendation for a description of virtual circuit states.

Interface

Interface or subinterface on which the virtual circuit is established.

Indicates that the X.25 D-bit (Delivery Confirmation) may be used on this circuit (displayed as needed).

Fast select VC

Indicates that the Fast Select facility was present on the incoming call (displayed as needed).

Reverse charged

Indicates reverse charged virtual circuit (displayed as needed).

Window size

Window sizes for the virtual circuit.

Packet size

Maximum packet sizes for the virtual circuit.

PS

Current send sequence number.

PR

Current receive sequence number.

ACK

Last acknowledged incoming packet.

Remote PR

Last receive sequence number received from the other end of the circuit.

RCNT

Count of unacknowledged input packets.

RNR

State of the Receiver Not Ready flag; this field is true if the network sends a Receiver-not-Ready packet.

Window is closed

This line appears if the router cannot transmit any more packets until the X.25 Layer 3 peer has acknowledged some outstanding packets.

P/D state timeouts

Number of times a supervisory packet (Reset or Clear) has been retransmitted.

Timer

A nonzero time value indicates that a control packet has not been acknowledged yet or that the virtual circuit is being timed for inactivity.

Reassembly

Number of bytes received and held for reassembly. Packets with the M-bit set are reassembled into datagrams for encapsulation virtual circuits; switched X.25 traffic is not reassembled (displayed only when values are non-zero).

Held Fragments/Packets

Number of X.25 data fragments to transmit to complete an outgoing datagram, and the number of datagram packets waiting for transmission (displayed only when values are non-zero).

data bytes m/n packets p/q

Total number of data bytes sent (m), data bytes received (n), data packets sent (p), and data packets received (q) since the circuit was established.

Resets t/r

Total number of Reset packets transmitted/received since the circuit was established.

RNRs t/r

Total number of Receiver Not Ready packets transmitted/received since the circuit was established.

REJs t/r

Total number of Reject packets transmitted/received since the circuit was established.

INTs t/r

Total number of Interrupt packets transmitted/received since the circuit was established.

1The ITU-T carries out the functions of the former Consultative Committee for International Telegraph and Telephone (CCITT).

The higher-level protocol and address values that are mapped to the virtual circuit.

Call PID

Identifies the method used for protocol identification (PID) in the Call User Data (CUD) field. Because PVCs are not set up using a Call packet, this field is not displayed for encapsulation PVCs. The available methods are as follows:

•cisco—Cisco's traditional method was used to set up a single protocol virtual circuit.

•ietf—The IETF's standard RFC 1356 method was used to set up a single protocol virtual circuit.

Identifies connection status for a switched connection between two PVCs. See Table 54 for PVC status messages.

170093

Identifies the Calling (source) Address of the connection. If a Calling Address Extension was encoded in the call facilities, it is also displayed. If the source host is a CMNS host, its MAC address is also displayed.

170090

Identifies the Called (destination) Address of the connection. If a Called Address Extension was encoded in the call facilities, it is also displayed. If the destination host is a CMNS host, its MAC address is also displayed.

from Serial1

Indicates the direction of the call and the connecting interface.

VC 5

Identifies the circuit type and LCN for the connecting interface. VC indicates an SVC, and PVC indicates a PVC. If the connecting host is a CMNS host, its MAC address is also displayed.

Locally Switched X.25 Traffic Between PVCs and SVCs Example

The following is sample output from the show x25 vc command used on a virtual circuit carrying locally switched PVC to SVC X.25 traffic:

Identifies the Calling (source) Address of the connection. If a Calling Address Extension was encoded in the call facilities, it is also displayed. If the source host is a CMNS host, its MAC address is also displayed.

201700

Identifies the Called (destination) Address of the connection. If a Called Address Extension was encoded in the call facilities, it is also displayed. If the destination host is a CMNS host, its MAC address is also displayed.

from Serial2

Indicates the direction of the call and the connecting interface.

VC 700

Identifies the circuit type and LCN for the connecting interface. VC indicates an SVC and PVC indicates a PVC. If the remote host is a CMNS host, its MAC address is also displayed.

Remotely Switched X.25 Traffic Example

The following is sample output from the show x25 vc command used on a virtual circuit carrying remotely switched X.25 traffic:

Identifies connection status for a switched connection between two PVCs. See Table 54 for PVC status messages.

170093

Identifies the Calling (source) Address of the connection. If a Calling Address Extension was encoded in the call facilities, it is also displayed.

170090

Identifies the Called (destination) Address of the connection. If a Called Address Extension was encoded in the call facilities, it is also displayed.

from

Indicates the direction of the call.

XOT between...

Identifies the IP addresses and port numbers of the X.25-over-TCP (XOT) connection.

Table 54 lists the PVC states that can be reported. These states are also reported by the debug x25 command in PVC-SETUP packets (for remote PVCs only) as well as in the PVCBAD system error message. Some states apply only to remotely switched PVCs.

Table 54 X.25 PVC States

Status Message

Description

awaiting PVC-SETUP reply

A remote PVC has initiated an XOT TCP connection and is waiting for a reply to the setup message.

can't support flow control values

The window sizes or packet sizes of the PVC cannot be supported by one of its two interfaces.

connected

The PVC is up.

dest. disconnected

The other end disconnected the PVC.

dest interface is not up

The target interface's X.25 service is down.

dest PVC config mismatch

The targeted PVC is already connected.

mismatched flow control values

The configured flow control values do not match.

no such dest. interface

The remote destination interface was reported to be in error by the remote router.

no such dest. PVC

The targeted PVC does not exist.

non-X.25 dest. interface

The target interface is not configured for X.25.

PVC/TCP connect timed out

A remote PVC XOT TCP connection attempt timed out.

PVC/TCP connection refused

A remote PVC XOT TCP connection was tried and refused.

PVC/TCP routing error

A remote PVC XOT TCP connection routing error was reported.

trying to connect via TCP

A remote PVC XOT TCP connection is established and is in the process of connecting.

waiting to connect

The PVC is waiting to be processed for connecting.

show x25 xot

To display information for all X.25 over TCP (XOT) virtual circuits that match a given criterion, use the show x25 xot EXEC command.

Examples

Related Commands

x25 address

To set the X.121 address of a particular network interface, use the x25 address interface configuration command.

x25 address x121-address

Syntax Description

x121-address

Variable-length X.121 address. It is assigned by the X.25 network service provider.

Defaults

Defense Data Network (DDN) and Blacker Front End (BFE) encapsulations have a default interface address generated from the interface IP address. For proper DDN or BFE operation, this generated X.121 address must not be changed. Standard X.25 encapsulations do not have a default.

Command Modes

Interface configuration

X.25 profile configuration

Command History

Release

Modification

10.0

This command was introduced.

Usage Guidelines

When you are connecting to a public data network (PDN), the PDN administrator will assign the X.121 address to be used. Other applications (for example, a private X.25 service), may assign arbitrary X.121 addresses as required by the network and service design. X.25 interfaces that engage in X.25 switching only do not need to assign an X.121 address.

Examples

The following example sets the X.121 address for the interface:

interface serial 0

encapsulation x25

x25 address 00000123005

The address must match that assigned by the X.25 network service provider.

x25 alias

To configure an interface alias address that will allow this interface to accept calls with other destination addresses, use the x25 alias interface configuration command.

Syntax Description

Regular expression used to match against the destination address of a received call.

x121-address-pattern

Alias X.121 address for the interface, allowing it to act as destination host for calls having different destination address.

cudcud-pattern

(Optional) Call user data (CUD) pattern, a regular expression of ASCII text. The CUD field might be present in a call packet. The first few bytes (commonly 4 bytes long) identify a protocol; the specified pattern is applied to any user data after the protocol identification.

Defaults

No alias is configured.

Command Modes

Interface configuration

X.25 profile configuration

Command History

Release

Modification

11.2

This command was introduced. It replaces the functionality that was provided by the alias keyword of the x25 route command.

Usage Guidelines

Encapsulation, packet assembler/disassembler (PAD), and Qualified Logical Link Control (QLLC) calls are normally accepted when the destination address is that of the interface (or the zero-length address). Those calls will also be accepted when the destination address matches a configured alias.

Examples

An X.25 call may be addressed to the receiving interface; calls addressed to the receiving interface are eligible for acceptance as a datagram encapsulation, PAD or QLLC connection, and may not be routed. In the following example, serial interface 0 is configured with a native address of 0000123 and a destination alias for any address that starts with 1111123. That is, serial interface 0 can accept its own calls and calls for any destination that starts with 1111123.